Magnetic device for use in an mpi apparatus

Abstract

The present invention relates to a magnetic device ( 400 a ) that can be localized and moved by a magnetic particle imaging apparatus, said magnetic device comprising a force-receiving portion ( 410 a ) formed by one or more ferromagnetic force-receiving elements, which force-receiving portion can be moved and/or oriented by use of magnetic fields, and a localization portion ( 420 a ) formed by one or more soft-magnetic localization elements arranged within or at a predetermined distance from said force-receiving portion, which localization portion provides response signals in response to the movement of a substantially field free area of a magnetic field over the location of the localization portion.

1 . A magnetic device that can be localized and moved by a magnetic particle imaging apparatus, said magnetic device comprising:
 a force-receiving portion formed by one or more ferromagnetic force-receiving elements, which force-receiving portion is arranged to be moved and/or oriented by use of magnetic fields and to move the magnetic device accordingly,   a localization portion formed by one or more soft-magnetic localization elements arranged within or at a predetermined distance from said force-receiving portion, which localization portion is arranged to provides response signals in response to the movement of a substantially field free area of a magnetic field over the location of the localization portion.   
     
     
         2 . The magnetic device as claimed in  claim 1 , 
       wherein said localization portion is arranged at a location at which the force receiving portion generates the lowest distortion of the magnetic fields applied for localization of the localization portion. 
     
     
         3 . The magnetic device as claimed in  claim 1 , 
       wherein said localization portion is arranged in a central area, in particular a symmetry center, within said force-receiving portion. 
     
     
         4 . The magnetic device as claimed in  claim 1 , 
       wherein said one or more localization elements comprise one or more soft-magnetic elements in the form of spheres, needles, patches, particles or foils. 
     
     
         5 . The magnetic device as claimed in  claim 1 , 
       wherein said one or more localization elements comprise at least two soft-magnetic elements arranged in a non-coplanar orientation with respect to each other. 
     
     
         6 . The magnetic device as claimed in  claim 1 , 
       wherein said localization portion further comprises a bearing, in particular a fluid bearing, allowing the one or more localization elements to align with a applied magnetic field. 
     
     
         7 . The magnetic device as claimed in  claim 1 , 
       wherein said one or more force-receiving elements comprise two or more ferromagnetic elements in the form of spheres arranged around said localization portion. 
     
     
         8 . The magnetic device as claimed in  claim 7 , 
       wherein said two or more ferromagnetic elements are arranged at the corners of a pyramid, in particular of a tetrahedron. 
     
     
         9 . The magnetic device as claimed in  claim 1 , 
       wherein said one or more force-receiving elements comprise a housing formed of a ferromagnetic material around said localization portion, said housing having a number of openings and/or slits. 
     
     
         10 . The magnetic device as claimed in  claim 1 , 
       wherein said one or more force-receiving elements are made of an annealed soft-magnetic material. 
     
     
         11 . The magnetic device as claimed in  claim 1 , 
       wherein said force-receiving portion is configured to change its magnetization, in particular configured to reduce its magnetization when the magnetic device shall be localized. 
     
     
         12 . The magnetic device as claimed in  claim 11 , 
       wherein said force-receiving portion comprises a switch, in particular an actuator or controller, to change the magnetization of the force-receiving portion. 
     
     
         13 . The magnetic device as claimed in  claim 1 , 
       wherein said force-receiving portion is made of anisotropic material, is formed in elongated form and/or comprises one or more permanent magnets. 
     
     
         14 . An apparatus for localizing and moving a magnetic device as claimed in  claim 13 , which apparatus comprises:
 selection means comprising a selection field signal generator unit and selection field elements for generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength where the magnetization of soft-magnetic localization elements of the magnetic device is not saturated and a second sub-zone having a higher magnetic field strength where the magnetization of soft-magnetic localization elements of the magnetic device is saturated are formed in the field of view,   drive means comprising a drive field signal generator unit and drive field coils for changing the position in space of the two sub-zones in the field of view by means of a magnetic drive field so that the magnetization of the soft-magnetic localization elements of the magnetic device changes locally,   focus means for changing the position in space of the field of view,   receiving means comprising at least one signal receiving unit and at least one receiving coil for acquiring detection signals, which detection signals depend on the magnetization in the field of view, which magnetization is influenced by the change in the position in space of the first and second sub-zone,   processing means for processing said detection signals, and   control means for controlling said selection means, said drive means and said focus means to generate magnetic fields to move the field of view to a position such that the magnetic device is positioned between a target position of the magnetic device and the center of the field of view in order to generate a force for moving the magnetic device in the direction of the target position and to thereafter or simultaneously move the field of view to a position such that the magnetic device is positioned within the field of view for localizing the magnetic device.   
     
     
         15 . The apparatus as claimed in  claim 14 , 
       wherein said control means is adapted to control said selection means, said drive means and said focus means to generate magnetic fields to alternately move the field of view into the position for generating a force onto the magnetic device for moving it into the direction of the target position and into the position for localizing the magnetic device until the magnetic device has reached the target position. 
     
     
         16 . A method for localizing and moving a magnetic device as claimed in  claim 13 , which method comprises:
 generating a magnetic selection fields having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength where the magnetization of soft-magnetic localization elements of the magnetic device is not saturated and a second sub-zone having a higher magnetic field strength where the magnetization of soft-magnetic localization elements of the magnetic device is saturated are formed in the field of view,   changing the position in space of the two sub-zones in the field of view, by means of a magnetic drive field so that the magnetization of the soft-magnetic localization elements of the magnetic device changes locally,   changing the position in space of the field of view,   acquiring detection signals, which detection signals depend on the magnetization in the field of view, which magnetization is influenced by the change in the position in space of the first and second sub-zone,   processing said detection signals, and   controlling the generation of magnetic fields to move the field of view to a position such that the magnetic device is positioned between a target position of the magnetic device and the center of the field of view in order to generate a force for moving the magnetic device in the direction of the target position and to thereafter or simultaneously move the field of view to a position such that the magnetic device is positioned within the field of view for localizing the magnetic device.